Improvement in processes for annealing and hardening metals



. 301m N. IIAUTH, or rrrrsnonarnnnsrmvnmn, nssienon'ro HIMsELF' AND ennrr, BENNETT & 00., or SAME rLAoE.

P IMPROVEMENT lN PROCESSES FOR ANNEALING AND HARDENING METALS.

Specification forming part of Letters Patent No. 1392,6535, dated October 29, 1872.

To all whom it may concern:

Be it known that I, Join: N. LAUTH, of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Annealing and Hardening Metals; and I do hereby declare the following to be a full, clear, and exact de-.

scription thereof.

One of the chief difficulties experienced in the annealing of metals, particularly where,

' as in imitation Russia sheet-iron, a fine polish or finish is desired, arises from the presence in the annealing-box of more or less air, which, acting on the metal, results in oxidation. The same trouble exists in the hardening of metals,

- particularly dies for stamping coin or other A hard substances where great perfeotness of die-face is required. I have found that such oxidation may be wholly prevented in annealing by heating and cooling in cacao, and in I necessary to use. finchbororvcssel' may be made of iron or other metals or composition of metals, or of fire-clay, plumbago, or other suitable material. I then exhaust the air as perfectly as possible from such box or receptacle by the use of an air-pump, or by other suitable means of producing a vacuum. The box or other receptacle with its contents, by heat applied externally, is raised to the desired temperature, after which it is allowed to cool gradually, as in the ordinary process of .annealing. The box can then be opened and the contents removed, fully annealed, and free from all trace of oxidation, except such, if any, as they may have had before being iuclosed in the box. In the process of hardening the operation is the same, except that after the box and contents have been raised to the desired temperature the latter are suddenly discharged into the water or oil or other fluid by which the process is tobe completed.

However, I find it better in this operation to employ a long box, somewhat like a pipe with closed ends, and for most purposes apipe will answer; The dies or other articles to be hardened are placed in one end, the box is hermetically closed, and the end containing the articles is inserted in the fire or furnace, the operator holding or manipulating it bythe other end. When the box and contents have been raised to the required temperature, the outer or unheated end may be placed in close proximity to'the water or oil or other fluid, the end of the box removed and the heated contents sufi'ered to fall directly into the flui so quickly that they will not be subject to e. oxidizing influence of the air long enough to be in- 1 juriously affected.

What I claim as my invention, and desire to secure by Letters Patent, is-

As an improvement in the art of hardening and annealing metals, subjecting the same, when free from atmospheric iufluence,to,the heating or heating and cooling operations, substantially as set forth.

In testimony whereof I, the said J DIIN N. LAUTH, have hereunto set my hand. 7

JOHN N. LAUTH,

lVitnesses:

- A. S. NIoHoLsON, JAMES I. KAY. 

